Scope: blow-moulded plastic drums for liquid dangerous goods, in particular closed-head (tight-head) drums under UN code 1H1. References: UN Recommendations on the Transport of Dangerous Goods — Model Regulations, Chapter 6.1, and GB 18191-2008, Packing containers — Plastic drums for packages of dangerous goods. A dangerous-goods (DG) drum differs from a general industrial drum not in appearance but in obligation: it must pass a full design-type test programme and carry inspection documents before it may bear the UN mark and be put into service.
DG drum testing is a two-stage system: type approval first, batch inspection second. A new drum design must pass the drop, leakproofness, hydraulic pressure and stacking tests (plus permeability and compatibility verification). Only then may it be issued a packing performance inspection certificate and bear the UN mark; routine production is then re-checked by batch sampling. When reviewing a supplier's report, first check that the packing group, test pressure and drop height in the report match the UN mark moulded on the drum itself.
No breakage of the drum, and no leakage of the contents from the closure once internal and external pressures have equalised.
Drop failures concentrate on the chime, the parting line and the base corner — exactly where parison wall-thickness distribution runs thin and mould pinching/welding runs weak. If a design fails the drop test, check the wall-thickness map and mould closing condition before blaming the resin.
The sample, complete with its closure, is restrained under water while internal air pressure is applied, and held for 5 minutes while watching for air bubbles. An equivalent leak-detection method may be used instead.
No leakage during the hold period (no continuous stream of bubbles underwater).
Leakproofness failures are almost always at the drum mouth and closure: mouth flatness, mouth diameter tolerance, gasket material and closing torque. On a factory audit, the mouth-dimension sampling records are worth a separate look.
The drum is filled with water and pressurised through a connected fitting. Once the specified test pressure is reached, it is held for 30 minutes (plastic drums). Pressure is applied continuously and evenly, and the way the drum is supported must not invalidate the test.
The test pressure is the greatest of the following three values, subject to two floors:
1. 1.5 times the total gauge pressure developed in the drum at 55 °C (vapour pressure of the contents plus partial pressure of air);
2. 1.75 times the vapour pressure of the intended liquid at 50 °C, minus 100 kPa;
3. 1.5 times the vapour pressure of the intended liquid at 55 °C, minus 100 kPa.
This is why two drums both marked for PG II can legitimately show different figures — 150 kPa on one report, 200 kPa on another — because the value depends on the liquid the design was qualified with. When reviewing a report, match its hydraulic figure against the three-digit number in the middle of the UN mark on the drum (that number is the hydraulic test pressure in kPa). If they disagree, ask why.
No leakage during the 30-minute hold, and no rupture or permanent deformation impairing strength.
A load is applied to the top of the sample equal to the total mass of identical filled packages that could be stacked on it in transport or storage, calculated on a minimum stacking height of 3 m including the sample itself. If the test liquid's density differs from that of the intended contents, the load is recalculated using the density of the intended contents.
No leakage after the test, and no collapse or deformation that would endanger the stability of the stack.
Stacking failure is a joint product of minimum wall thickness and resin stiffness (density, melt flow). It shows up first in the lower sidewall and the recessed base. Holding the wall-thickness floor with proper parison control saves more material — and works better — than thickening the whole drum.
An export DG drum carries an embossed or printed mark along these lines (illustrative example):
UN 1H1/Y1.9/150/26/CN/PI0000
Reading it segment by segment:
The most useful receiving check is a three-way match: packing-group letter, relative density and hydraulic value on the mark, against the performance certificate and the design-type test report. All three must agree.
1. Request the design-type test report and confirm that packing group, drop height, leakproofness pressure and hydraulic pressure cover the goods you intend to fill.
2. Request the packing performance certificate; confirm it is in date and that the drum type matches the report.
3. Sample-check the UN mark on delivered drums against the documents, item by item (group letter, relative density, hydraulic value, year, manufacturer code).
4. Confirm the qualification conditions: which liquid and which density the design was tested with. If your liquid's density or vapour pressure exceeds the qualified range, the design must be re-assessed — "DG approved" is never generic.
5. On a factory audit, review three records: wall-thickness measurement points, cold drop-test sampling records, and resin grade/batch traceability.
6. Verify the closure separately: gasket material and cap specification must match the closure used in the approved design type. Changing the cap means changing the design type.
General chemical and food drums are batch-sampled against a product standard (such as GB/T 13508) and leave it at that: no −18 °C cold drop, no 28-day hot stacking, no UN mark and no DG certificates. If your goods appear on a dangerous-goods list, receive the drums to DG requirements — never to general-drum standards.
*Sources: GB 18191-2008, Packing containers — Plastic drums for packages of dangerous goods; UN Recommendations on the Transport of Dangerous Goods — Model Regulations, Chapter 6.1. Compiled by Shandong Tongjia Intelligent Equipment Co., Ltd., November 2026.*
